Strapping machines are well known in the art. Typically these machines are used for securing straps around loads. One type of strapper is used with a plastic or polymeric strap and is a stationary arrangement in which the strapper is included as part of an overall manufacturing or packaging system.
A typical strapper includes a frame to which various components are mounted. A chute is mounted to the frame through which the strapping material is fed around a load. A strapping head and a drive or feed mechanism are mounted to the frame. The strapping material is fed from a source, by the feed assembly, through the strapping head. The strapping material traverses around the chute and back to the strapping head. Various guides may be mounted to the frame to provide a path for the strap. For example, a guide may be positioned at the feed assembly to guide the strap into feed wheels. A guide may also be positioned between the feed assembly and the strapping head to provide a strap path from the feed assembly to the head.
The strapping or welding head provides a number of functions. First, the strapping head includes a gripper having one or more gripper portions that grip the strap during the course of a strapping operation. The strapping head also includes a cutter to cut the strap from a strap source or supply. Last, the strapping head includes a sealer to seal an overlying course of strapping material onto itself. This seal is commonly referred to as a weld and is effected by heating one course of the strap by use of a vibrating element.
Known strapping heads include a body and an anvil between which the courses of strap materials traverse during a strapping operation and between which the strapping material courses are held during the welding operation. The gripper is mounted within the body and is operably connected to a camshaft having a plurality of cams thereon. Cam lobes move the gripper into and out of engagement with the strapping material to effect the necessary gripping functions during the strapping operation. The anvil is maintained rigidly against the body and a vibrating element within the body oscillates or vibrates thus creating friction and heat to effect the weld.
The vibrating element is disposed within the strapping head body. During the course of welding the strapping material onto itself, the gripper must maintain a sufficient pressure on the strap, against the anvil, to assure that the strap does not slip as the vibrating element vibrates (i.e., as the seal is made). To this end, complex linkages are required to assure that the gripper (mounted within the body) maintains contact with the strap (and the anvil) when the vibrating element is actuated. As such, strapping heads can be of complex, construction and design, particularly when large tensions are required in the strap to maintain the load bundled.
Accordingly, there exists a need for a simplified welding or strapping head for use in a strapping machine. Desirably, such a welding head eliminates the need for complex linkages otherwise required to maintain the gripping portion in contact with the strap (and the anvil) when the vibrating element is actuated. More desirably, such a strapping head is of a compact design. Most desirably, in such a strapping head, the vibrating element is removed from the strapping head body.
A strapping head is used in a strapping machine of the type having a feed assembly and a chute. The strapping machine is configured to position, tension and seal strapping material around a load. The strapping head is positioned adjacent the chute.
The strapping head includes a body and an anvil mounted to and movable relative to the body. In a present embodiment, strapping head includes a side plate pivotally mounted to the body and the anvil is fixedly mounted to the side plate.
The strapping head further includes a gripper assembly disposed in the body and a sealing member disposed in the anvil for oscillating movement. A drive is operably connected to the sealing member to provide oscillating movement to the sealing member.
First and second courses of strapping material overlie one another in the strapping head, adjacent the sealing member. Oscillation of the sealing member effects a seal of the first and second courses of strapping material to one another.
In a preferred configuration, the sealing member drive is mounted to the side plate for movement with the anvil. To effect oscillation, the drive includes an eccentric drive element and the sealing member include a coupling portion for coupling with the eccentric drive element. The eccentric drive element can be configured as an eccentric shaft and the coupling portion can include a non-circular receiving opening for receiving the shaft. In such a configuration, a bearing is disposed on the shaft for contact with the receiving opening.
To accommodate the sealing member, the anvil includes a channel formed therein. Bearings can be disposed within the channel for receiving the sealing member.
The strapping head can include a platen for maintaining the first and second courses of strapping material compressed against the sealing element. The platen can be disposed between first and second grips within the gripper assembly, with the cutter disposed adjacent the platen.
These and other features and advantages of the present invention will be apparent from the following detailed description, in conjunction with the appended claims.